1. Field of the Invention
The present invention relates to a seat belt buckle used for a safety belt of an automobile or aircraft, and particularly to seat belt buckle in which a so-called measure to counter reverse G is taken.
2. Description of the Related Art
Generally, the above-described type of seat belt buckle is disclosed in, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 60-18102, 60-75004, and 60-75005. In these buckles disclosed therein, a tongue plate is latched with the buckle such that a latch member of the buckle is engaged with a latch engaging hole of the tongue plate by inserting, into a buckle main body, an end of the tongue plate through which a seat belt (webbing) is inserted to pass. Further, the latched state is locked by a locking member and coming-off (ejection) of the tongue plate from the buckle main body is prevented.
When the locking state of the latch is cancelled by a pressing operation of a release button, latch engagement is cancelled and the tongue plate is made to come off from the buckle main body.
The above-described type of seat belt buckle is structured in such a manner that after the tongue plate is once inserted into the buckle main body completely to a lock position and locked, even if an impact is applied to the buckle, the tongue plate can be reliably held in a locked state without a latched and locked state of the tongue plate being cancelled. For example, the latch is constantly spring-urged (pressed) by a spring member toward the lock position, and the release button is returned to an original position. The release button for releasing the latched and locked state is structured so as to be able to be pressed by a small force.
Recently, safety devices have been proposed, wherein at the time of accidents such as a vehicle colliding with another vehicle or an obstacle, the buckle itself by which the tongue plate is locked, is instantaneously pulled due to instantaneous force such as explosion pressure of gunpowder and looseness of the seat belt is removed into a state of strain, thereby preventing various troubles caused by looseness of the seat belt.
However, when the buckle itself by which the tongue plate is locked is thus instantaneously pulled, so-called reverse G occurs in the buckle. Therefore, in a conventional buckle, even when the release button is not pressed, there may be a risk of the tongue plate being made to come off due to the locked state by the latch being cancelled. In other words, when the buckle itself is instantaneously and strongly pulled in a direction in which the seat belt is tensed, at the time of that the seat belt is tensed to the utmost, pulling of the buckle itself, that is, a case of a buckle main body is forcedly and rapidly stopped. Therefore, an inertia force corresponding to the total mass of the release button, locking mechanism, and the like which are accommodated within the case of the buckle main body in a state of being freely pressed, acts on the release button, locking mechanism and the like in a direction in which the lock state is released. As a result, there is a problem that the lock state may be forcedly cancelled and the tongue plate may come off form the buckle main body.
Accordingly, in order to prevent the tongue plate from coming off, in the conventional seat belt buckle, a method has been provided, wherein a spring force of the spring, which constantly urges the latch to a lock position by pressing, is increased. However, in this case, the spring becomes larger in size, and pressing force, that is, release force of the release button for releasing the locking state of the latch against spring force of the spring, may be increased.
In view of the above-described circumstances, an object of the present invention is to provide a seat belt buckle which can prevent coming-off of a tongue plate caused by so-called reverse G without increasing release force for canceling a lock state.
A first aspect of the present invention is a seat belt buckle comprising: a base including an insertion path in or from which a tongue plate having an engagement hole is inserted or removed, a pair of upright side walls, each of the side walls disposed at respective sides of the insertion path, and an engagement hole; a latch including latch lug portions supported swingably by supporting portions formed in the side walls of the base, and a latch swinging end portion swinging between a latch position at which, when the tongue plate is inserted to a latch position of the insertion path, the latch swinging end portion engagingly inserted into both of the engagement hole of the tongue plate and the engagement hole of the base so as to latch the tongue plate to the base, and a latch release position at which a latched state is released; a lock member including lug portions inserted swingably into supporting holes formed in the side walls of the base, a lock swinging end portion swinging between a lock position at which, at the time of the latched state, the lock swinging end portion latches (abuts) the latch swinging end portion in a state in which the latch swinging end portion is pressed toward both of the engagement hole of the tongue plate and the engagement hole of the base while the latch swinging end portion is pressed in a direction in which the tongue plate is inserted, thereby locking the latched state, and a lock release position at which a locked state is released; a lock sliding portion swinging together with the lock swinging end, and during swinging, sliding on the latch swinging end; a lock operation end portion which is located at the side opposite to the lock swinging end portion with respect to the lug portions interposed therebetween, and by which, when the lock operation end portion is pressed in the direction in which the tongue plate is inserted at the time of locking, the lock swinging end portion is made to swing to the lock release position, thereby releasing the lock state, and a weight portion by which a center of gravity of the lock member is made more eccentric to the lock swinging end portion than the lug portions; a latch spring elastically pressing, at the time of locking, the lock swinging end portion of the lock member substantially in the direction in which the tongue plate is inserted, to maintain the locked state; a release button including sliding portions mounted in elongated holes formed in the side walls of the base in a slidable manner in directions in and from which the tongue plate is inserted and removed, and a button which, when pressed against spring force of the latch spring in the direction in which the tongue plate is inserted, presses the lock operation end portion of the lock member in the direction in which the tongue plate is inserted, and causes the lock swinging end portion to swing in the direction from which the tongue plate is removed, thereby releasing the locked state; and an ejector which, when pressed by the tongue plate to a latch position, guides to fit the latch swinging end portion into the engagement hole of the tongue plate and the engagement hole of the base to allow latching and locking, and which, when the locked state is released by pressing the release button, presses the latch swinging end portion to the latch release position to release the latched state and removes the tongue plate from the insertion path of the base.
According to the above-described aspect of the present invention, the lock swinging end of the lock member presses to lock the latch swinging end of the latch for latching the tongue plate toward the engagement hole while pressing the same (from the front side (i.e., upstream side) to the rear side (i.e., downstream side)) in the direction in which the tongue plate is inserted. Therefore, when so-called reverse G occurs, that is, when an inertia force is generated due to rapid stopping of instantaneous pulling of the base, the inertia force acts on the lock swinging end (from the front side to the rear side) in the direction in which the tongue plate is inserted, i.e., the direction in which the latch swinging end is pressed by the lock swinging end at the time of locking. Accordingly, the lock state can be rather reinforced.
Further, the center of gravity of the lock member is located nearer the lock swinging end than the lock operation end, and the mass of the lock member at the side of the lock swinging end is made larger by the weight portion. Therefore, the inertia force acting on the lock swinging end in the locking direction can be made larger than the inertia force acting on the release button in the direction in which locking is released. Accordingly, the lock state of the latch can be held more firmly by the lock member. As a result, it is possible to reliably prevent ejection of the tongue plate when a pressing operation of the release button is not done, and safety of the seat belt buckle can be improved so much.
Moreover, the lock swinging end of the lock member for locking the latch state of the latch is urged by the latch spring in the direction in which the lock state is reinforced, i.e., the direction in which the tongue plate is inserted. In addition, no spring member for urging the latch in a direction opposite to the direction in which the tongue plate is inserted, is provided, unlike a conventional structure. Therefore, in the conventional structure, it is necessary that the lock state of the latch be released by pressing the release button against the spring force of this spring member (therefore, large pressing force of the release button is needed). However, in the present invention, it is not necessary that the lock state of the latch be released by pressing the release button against the spring force in the direction in which the tongue plate is inserted. As a result, pressing force of the release button, that is, release force can be alleviated, and safety can be further improved.
A second aspect of the present invention is a seat belt buckle according to the first aspect, wherein the supporting holes formed in the side wall of the base, into which the lug portions of the lock member are inserted, are each made circular, and at each of the side walls, an introduction groove is formed so as to communicate with the supporting hole and have an opening at an external end of the side wall.
According to the above-described aspect of the present invention, the pair of lug portions of the lock member can be simply inserted into the supporting holes in such a manner as to be put in respective open ends of the pair of introduction grooves formed in the side walls of the base and inserted along the introduction grooves. That is, assembly workability for mounting the lock member in the base can be improved.
A third aspect of the present invention is a seat belt buckle according to the first or the second aspect, wherein the lock member is structured in such a manner that the lug portions, the lock swinging end portion, the lock sliding portion, the lock operation end portion, and the weight portion are formed integrally by press forming of a metal flat plate.
According to the above-described aspect of the present invention, the lock member is entirely formed by press forming of a metal flat plate. Therefore, as compared with a case in which the lock member is formed from sintered metal, improvement in simplicity of manufacture and reduction in cost can be both achieved.
A fourth aspect of the present invention is a seat belt buckle according to any one of the first to third aspect, wherein the lock sliding portion includes two lock sliding portions which are respectively formed at both ends of the lock swinging end portion in a transverse direction of the lock member, and a sliding surface of each of the lock sliding portions, which slides on respective transverse-direction ends of the latch swinging end portion in directions in and from which the tongue plate is inserted and removed, is formed into a circular arc.
According to the above-described aspect of the present invention, the lock sliding portions of the lock member sliding on the latch swinging end of the latch are respectively formed at two places, i.e., at both transverse-direction ends of the lock member. Therefore, as compared with a case of sliding at one place, a sliding operation when the sliding portions of the lock swinging end slide on both transverse-direction ends of the latch swinging end, can be stabilized, and the locked state of the latch can also be stabilized. As a result, safety can be improved.
Further, the lock sliding portions sliding on both transverse-direction ends of the latch swinging end each has the circular arc-shaped sliding surface. Therefore, the each contact area of the sliding surface decreases and sliding loss can be reduced. As a result, force by which the tongue plate is inserted into the insertion path to allow swinging of the lock swinging end, and pressing force of the release button (i.e., release force) can be alleviated.
A fifth aspect of the present invention is a seat belt buckle according to any one of the first to fourth aspect, wherein the lock sliding portions of the lock member each include a sliding surface which abuts against and slides on the latch swinging end portion when the latched state is released, and the sliding surface is formed as a circular-arc surface recessed inward.
According to the above-described aspect of the present invention, in a latch release state, the latch swinging end abuts against respective one surfaces, for example, rear surfaces, of the lock sliding portions of the lock member and rotates around the central axis of swinging of the latch swinging end. The sliding surface of each lock sliding portion is formed into a concave arcuate surface, and therefore, the latch swinging end can rotate smoothly around the central axis of swinging thereof in a state of slide-contacting the concave arcuate surfaces. Accordingly, the sliding loss of the latch swinging end can be reduced. Further, the latch sliding portions are each constantly made to partially slide-contact one surface of the lock sliding portion. Therefore, shaking of the latch swinging end (unstability of the latch swinging end) is prevented and a latch release operation can be stabilized.
A sixth aspect of the present invention is a seat belt buckle according to any one of the first to fifth aspect, wherein the lock member is mounted on a stopper made of resin and having a spring-mounting notch portion, and one end of a latch spring is engaged with the spring-mounting notch portion of the stopper.
According to the above-described aspect of the present invention, the lock member, the stopper, and the latch spring are in advance assembled in such a manner that the stopper made of synthetic resin is mounted in the lock member and one end of the latch spring is engaged with the supporting notches of the stopper, and the prefabricated component thus formed can be mounted in the base. As a result, the number of assembling processes of the seat belt buckle can be reduced and assembly workability for mounting the lock member in the base can be improved.
Further, the stopper is made of synthetic resin having elasticity, and therefore, it can be mounted, by fitting, in the lock member made of metal simply, reliably, and rapidly. In addition, the degree at which both members are mounted integrally and closely can be increased. Moreover, the latch spring inserted in the supporting notches of the stopper can be simply and reliably mounted in the lock member at a predetermined mounting position with high accuracy.
A seventh aspect of the present invention is a seat belt buckle according to the sixth aspect, wherein the stopper includes stopper portions formed integrally therewith and abutting against the sliding portions of the release button in the locked state.
According to the above-described aspect of the present invention, the stopper portions of the stopper engaged with and mounted in the lock member abut against the sliding portions of the release button at the time of locking. Therefore, it is possible to prevent the lock state from being released without pressing the release button, which is caused by shaking (usstability) of the lock member at the time of locking. Safety can be improved so much.
A eighth aspect of the present invention is a seat belt buckle according to the first or second aspect, wherein the lock member comprises a lock-member main body portion including lug portions, lock swinging end portion, a lock operation end portion, and stopper portions abutting against the sliding portions of the release button in the locked state, all of which are formed integrally by press forming of a metal flat plate, and a lock-member weight portion including a weight portion and a pair of lock sliding portions located at both transverse-direction ends of the weight portion, the weight portion and the lock sliding portions being formed integrally by press forming of a metal flat plate, wherein lock-member main body portion further includes spring-mounting notch portion in which one end of the latch spring is engaged, and the lock-member weight portion is attachably-and-removably mounted in the lock-member main body portion.
According to the above-described aspect of the present invention, the lock-member weight portion attachably and removably mounted in the lock-member main body portion is made of metal. Therefore, mechanical strength can be increased and the mass of the weight portion itself can also be increased.
As a result, the mass at the side of the lock swinging end can be made larger than the mass at the side of the lock operation end. Therefore, when so-called reverse G occurs, the inertia force acting on the lock swinging end in the locking direction can be increased still more. Accordingly, the lock state of the latch can be held more firmly by the lock member. Therefore, it is possible to prevent ejection of the tongue plate more reliably when a pressing operation of the release button is not done, and safety of the seat belt buckle can be improved so much.
Further, the lock-member main body portion, the lock-member weight portion, and the latch spring are in advance assembled in such a manner that the lock-member weight portion is mounted in the lock-member main body portion and one end of the latch spring is engaged with the mounting notches of the lock-member main body portion, and the prefabricated component comprised of the three portions can be mounted in the base. As a result, the number of assembling processes of the seat belt buckle decreases and assembly workability for mounting the lock member in the base can be improved.
The pair of lock sliding portions of the lock-member weight portion sliding on the latch swinging end are respectively formed at two places, i.e., at both transverse-direction ends of the lock-member weight portion. Therefore, as compared with a case of sliding at one place, a sliding operation when the pair of lock sliding portions slide on both transverse-direction ends of the latch swinging end, can be stabilized, and the locked state of the latch can also be stabilized. As a result, safety can be improved.
A ninth aspect of the present invention is a seat belt buckle according to the eighth aspect, wherein the lock-member main body portion includes the stopper portions formed integrally therewith and abutting against the sliding portions of the release button in the locked state.
According to the above-described aspect of the present invention, the stopper portions formed integrally with the lock-member main body portion abut against the sliding portions of the release button at the time of locking. Therefore, it is possible to prevent the lock state from being released without pressing the release button, which is caused by shaking (for example, unstsbility) of the lock member at the time of locking, and safety can be improved so much.
Further, the stopper portions are formed integrally with the lock-member main body portion made of metal. Therefore, the strength of the stopper portions can be increased, and reliability of stopper function of the stopper portions can be improved so much. Accordingly, safety of the seat belt buckle can be improved.
A tenth aspect of the present invention is a seat belt buckle according to the eighth or ninth aspect, wherein the lock sliding portions of the lock-member weight portion each include a sliding surface which slides on the latch swinging end portion in directions in and from which the tongue plate is inserted and removed, and each sliding surface is formed into a circular arc.
According to the above-described aspect of the present invention, the pair of lock sliding portions sliding on both transverse-direction ends of the latch swinging end each have a sliding surface formed into a circular arc. Therefore, a contact area of the sliding surface decreases and the sliding loss can be reduced. As a result, force by which the tongue plate is inserted into the insertion path to allow swinging of the lock swinging end, and pressing force of the release button (i.e., release force) can be alleviated.
A eleventh aspect of the present invention is a seat belt buckle according to any one of the first to tenth aspect, wherein the lock member includes an insertion hole at the lock operation end portion, and the release button includes an inserting projection which is inserted into the insertion hole of the lock operation end portion at a time of pressing the release button, and at the same time, presses the lock operation end portion so as to swing the lock swinging end portion to the lock release position while gradually lifting the lock swinging end portion in a direction opposite to a direction in which it is pressed toward the latch swinging end portion.
According to the above-described aspect of the present invention, when the release button is pressed, the inserting projection of the release button is gradually inserted into the insertion hole of the lock member and the lock member is gradually lifted by an inclined surface of the inserting projection in a direction opposite to a pressing direction toward the latch swinging end. The pressing force is reduced, and thereafter, the lock swinging end of the lock member are made to swing to the lock release position. Accordingly, the pressing force of the release button, that is, release force can be alleviated still further.
A twelfth aspect of the present invention is a seat belt buckle according to any one of the first to eleventh aspect, wherein the sliding portions of the release button are provided at respective ends of a pair of arms formed so as to hold therein the side walls of the base from externally, and a guide groove is formed in the each of the sliding portions in such a manner that an open edge of an elongated hole provided in each of the side walls of the base is slidably fitted therein.
According to the above-described aspect of the present invention, the pair of arms of the release button are formed in the transverse direction of the release button so as to hold therein the pair of side walls of the base from externally, and the sliding portions at respective ends of the arms are made to slide in the elongated holes of the side walls of the base. Therefore, the sliding operation of the sliding portions when the release button is pressed can be stabilized in the transverse direction of the release button and can be made smooth.
Further, the sliding portions of the release button, which is fitted slidably into the elongated hole of the base, are each provided with a guide groove into which an open edge of the elongated hole is slidably fitted. Therefore, the open edge of the elongated hole can be slidably held by the pair of facing walls of the guide groove. As a result, removal of the sliding portion from the elongated hole can be prevented.
A thirteenth aspect of the present invention is a seat belt buckle according to any one of the first to twelfth aspect, wherein the release button is entirely formed from synthetic resin.
A fourteenth aspect of the present invention is a seat belt comprising: a base including an insertion path in or from which a tongue plate having an engagement hole is inserted or removed, and a pair of upright side walls, each of the side walls disposed at respective sides of the insertion path; a latch supported swingably at the side walls of the base, and swinging between a latch position at which, when the tongue plate is inserted to a latch position of the insertion path, the latch engagingly inserted into the engagement hole of the tongue plate so as to latch the tongue plate, and a latch release position at which a latched state is released; a lock member including a lock swinging end portion swinging between a lock position at which, at the time of the latched state, the lock swinging end portion latches (abuts) the latch in a state in which the latch is pressed toward the engagement hole of the tongue plate while the latch swinging end portion is pressed in a direction in which the tongue plate is inserted, thereby locking the latched state, and a lock release position at which a locked state is released; a lock sliding portion swinging together with the lock swinging end, and during swinging, sliding on the latch; a lock operation end portion by which, when the lock operation end portion is pressed in the direction in which the tongue plate is inserted at the time of locking, the lock swinging end portion is made to swing to the lock release position, thereby releasing the locked state, and a weight portion by which a center of gravity of the lock member is made eccentric to a lock swinging end portion side; a latch spring elastically pressing, at the time of locking, the lock swinging end portion of the lock member substantially in the direction in which the tongue plate is inserted, to maintain the locked state; a release button including a button which presses the lock operation end portion of the lock member in the direction in which the tongue plate is inserted, and causes the lock swinging end portion to swing in the direction from which the tongue plate is removed, thereby releasing the locked state; and an ejector which, when the locked state is released by pressing the release button, presses the latch to the latch release position to release the latched state and removes the tongue plate from the insertion path of the base.
According to the above-described aspect of the present invention, the release button is entirely lightened by being formed from synthetic resin. Therefore, when so-called reverse G occurs, the inertia force acting on the release button in the pressing direction can be reduced greatly as compared with the inertia force acting on the lock swinging end of the lock member in the locking direction. As a result, it is also possible to prevent ejection of the tongue plate from the buckle when so-called reverse G occurs. Further, safety can be improved.